[Tropical] Tropical Weather Discussion

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AXNT20 KNHC 171135
TWDAT

TROPICAL WEATHER DISCUSSION
NWS TPC/NATIONAL HURRICANE CENTER MIAMI FL
705 AM EST SAT NOV 17 2007

TROPICAL WEATHER DISCUSSION FOR NORTH AMERICA...CENTRAL
AMERICA...THE GULF OF MEXICO...THE CARIBBEAN SEA...NORTHERN
SECTIONS OF SOUTH AMERICA...AND THE ATLANTIC OCEAN TO THE
AFRICAN COAST FROM THE EQUATOR TO 32N. THE FOLLOWING INFORMATION
IS BASED ON SATELLITE IMAGERY...METEOROLOGICAL ANALYSIS...
WEATHER OBSERVATIONS...AND RADAR.

BASED ON 0600 UTC SURFACE ANALYSIS AND SATELLITE IMAGERY THROUGH
1115 UTC.

...TROPICAL WAVES...
TROPICAL WAVE APPEARS TO HAVE PICKED UP SOME SPEED AS IT
APPROACHES THE WINDWARD ISLANDS NOW CLOSE TO 60W S OF 16N MOVING
W 15-20 KT. THIS WAVE HAS GAINED CONVECTION OVERNIGHT WITH
LATEST IR IMAGES REVEALING SCATTERED MODERATE FROM 9N-12N
BETWEEN 57W-61W. BUOY DATA IN THE REGION SHOWS A PRES MINIMUM
NEAR THE WAVE AXIS AND AN EARLIER QSCAT PASS DEPICTED A SLIGHT
INCREASE IN THE ELY TRADES ALONG AND TO THE E OF THE WAVE AXIS.

TROPICAL WAVE IS IN THE CENTRAL CARIBBEAN ALONG 76W S OF 17N
MOVING W 10-15 KT. THE MIMIC TPW ANIMATION PROVIDES A BIT OF
HISTORY ON THIS WAVE SHOWING A WELL DEFINED...ALBEIT
NARROW...MOISTURE PLUME TRACKING WWD ACROSS THE CARIB THU AND
EARLY FRI. THIS MOISTURE AREA...WHICH IS THOUGHT TO REPRESENT
MUCH OF THE WAVE ENERGY...HAS BEEN PULLED TO THE NE BY A STRONG
COLD FRONT OVER THE LAST 12-18 HOURS. THE LEFT OVER PORTION OF
THE WAVE IS WEAK AND IS ONLY PRODUCING ISOLATED SHOWERS IN ITS
VICINITY.

...THE ITCZ...
ITCZ AXIS IS CENTERED ALONG 8N13W 6N26W 7N40W 8N56W. SCATTERED
MODERATE CONVECTION IS WITHIN 90 NM N OF THE AXIS BETWEEN
26W-33W AND WITHIN 240 NM S OF THE AXIS BETWEEN 33W-39W.
SCATTERED MODERATE IS ALSO WITHIN 120 NM N OF THE AXIS BETWEEN
47W-53W.

DISCUSSION...

THE GULF OF MEXICO...
SFC HIGH PRES CONTINUES TO SHIFT E CENTERED OVER THE
GEORGIA/FLORIDA BORDER NEAR 31N85W...ANALYZED 1022 MB. ITS A
VERY CHILLY MORNING E OF THE HIGH ACROSS PORTIONS OF THE
SOUTHEAST WITH TEMPS AS COLD AS THE MID TO UPPER 20'S F IN THE
TYPICAL COOLER INLAND PORTIONS OF NW FLORIDA. THE AIRMASS
MODIFIES FURTHER W ESPECIALLY W OF 90W WHERE LOW-LEVEL RETURN
FLOW HAS SET UP. FAIR WEATHER EXISTS ACROSS THE ENTIRE AREA WITH
SATELLITE IMAGERY SHOWING COOL AIR STRATOCUMULUS CLOUDS AS THE
PRIMARY MOISTURE SOURCE IN THE CENTRAL AND E GULF AND SOME
PATCHY LOW TO MID LEVEL CLOUDS IN FAR WRN PORTION...PICKED UP BY
THE MORE MOIST LOW-LEVEL FLOW. IN THE MID AND UPPER LEVELS
...MODEST RIDGING AND ABUNDANT STABLE AIR COVERS THE REGION.
LOOKING AHEAD A DAY OR TWO...SFC HIGH PRES IS EXPECTED TO
CONTINUE TRACKING EWD ALLOWING E TO SE FLOW TO DEVELOP WHICH
WILL ALLOW TEMPS TO RECOVER BACK TOWARD NORMAL.

THE CARIBBEAN SEA...
STRONG COLD FRONT THAT SWEPT THROUGH THE GULF OF MEXICO THU AND
FRI IS GRADUALLY LOSING ITS IDENTITY IN THE NW CARIBBEAN
...ANALYZED FROM ERN CUBA TO THE CENTRAL YUCATAN COAST. COOL AIR
HAS WORKED ITS WAY AS FAR S AS THE NRN YUCATAN WITH TEMPS
IMPRESSIVELY AS LOW AS THE UPPER 50'S F IN CANCUN. THERE IS SOME
PATCHY LOW-LEVEL CLOUDINESS AND ISOLATED SHOWERS WITHIN 60 NM OF
THE FRONT. FARTHER S...IR IMAGERY SHOWS SMALL CLUSTERS OF
SHOWERS AND ISOLATED TSTMS IN THE SW CARIB FROM 9N-12N BETWEEN
79W-83W ASSOCIATED WITH LOW-LEVEL CONFLUENCE NEAR THE ITCZ.
SIMILAR WEATHER IS OCCURRING OVER HISPANIOLA AND NEARBY WATERS
TIED TO THE TAIL END OF A PRE-FRONTAL TROUGH. SAN JUAN DOPPLER
RADAR...WHICH WAS ACTIVE EARLIER...SHOWS NEARLY ALL OF THE
ACTIVITY W OF THE ISLAND. SCATTERED SHOWERS AND TSTMS ARE ALSO
MAKING THEIR WAY TOWARD THE WINDWARD ISLANDS TRIGGERED BY
APPROACHING TROPICAL WAVE. THE REMAINDER OF THE AREA IS
RELATIVELY TRANQUIL WITH MODERATE DRY AIR AND SW TO ZONAL FLOW
OVERHEAD.

THE ATLANTIC OCEAN...
MID AND UPPER LEVEL TROUGHING DOMINATES MUCH OF THE WRN ATLC
EXTENDING SWD FROM A POLAR VORTEX. THIS UPPER SYSTEM IS
SUPPORTING A FAIRLY STRONG COLD FRONT WHICH STRETCHES FROM
32N58W ACROSS THE SE BAHAMAS. THE COMBINATION OF SFC HIGH PRES
BEHIND THE FRONT AND A VERY DRY ENVIRONMENT ALOFT IS PROVIDING
FAIR AND COOL WEATHER ACROSS THE SW ATLC. NIGHT CHANNEL VIS
IMAGERY SHOWS A LARGE AREA OF SCATTERED STRATOCUMULUS
CLOUDS...INDICATIVE OF THE COOL AIRMASS IN PLACE. SOME ACTIVE
WEATHER LIES IN A DIFFLUENT ZONE ALOFT BETWEEN THE TROUGH AND A
RIDGE AXIS ALONG 50W/51W. IR IMAGES AND LIGHTNING DATA REVEAL
SCATTERED SHOWERS AND TSTMS N OF 23N BETWEEN 52W-60W AND S OF
20N BETWEEN 66W-70W. A SFC PRE-FRONTAL TROUGH FROM 26N58W TO THE
DOMINICAN REPUBLIC
IS ENHANCING SOME OF THIS WEATHER ESPECIALLY S OF 20N.

PART OF THE CENTRAL ATLC...BETWEEN 40W AND 53W...IS DOMINATED BY
DEEP LAYER RIDGING AND DEBRIS HIGH LEVEL CLOUDINESS. THE PATTERN
QUICKLY CHANGES THEME IN THE E ATLC WHERE LARGE SCALE DEEP LAYER
TROUGHING IS IN PLACE ANCHORED BY AN OCCLUDED LOW NEAR 35N28W. A
MID-LEVEL DISTURBANCE TO THE S OF THE OCCLUDED LOW APPEARS TO
HAVE BUILT DOWN TO THE SFC AND A 1011 MB LOW WAS ADDED TO THE
MAP NEAR 25N31W AT 06Z. THIS LOW LIES ALONG A FRONT EXTENDING
FROM A 1005 MB LOW W OF THE MADEIRA ISLANDS NEAR 34N20W TO
24N42W. ASSOCIATED SCATTERED SHOWERS AND TSTMS HAVE BECOME
INCREASINGLY STRETCHED FROM 23N-29N BETWEEN 26W-32W. A SWLY JET
BRANCH HAS SET UP NEAR THE BASE OF THE TROUGH AND THEN RUNS NE
ALONG 14N47W 17N30W 24N22W GENERATING AND ADVECTING MID-HIGH
LEVEL CLOUDINESS WITHIN 150 NM SE OF THE JET AXIS.

$$
CANGIALOSI


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